energy. If the photoactive semiconductor electrode can simultaneously store photoexcited charges in situ via reversible cation intercalations, the photoelectrode system can be developed into a solar-intercalation battery, enabling direct conversion and storage of solar energy in the battery electrode. [3][4][5][6][7] Solar-intercalation batteries offer several advantages. First, they are inherently simple systems since they do not require complex installations for the storage and distribution of fuels, e.g., solar fuels. Second, they are potential energy efficient devices in that they utilize a single material photoactive host electrode for the dual functionalities of energy harvesting and storage, thereby eliminating any possibility of energy losses associated with charge transfer. Third, they can be highly robust if they are developed as small and portable energy devices with capacities to bridge the energy needs of a day and night cycle. Solar-intercalation batteries are unlike systems where solar energy harvesting and energy storage are achieved by separate or hybrid technologies. [8,9] For instance, a photovoltaically selfcharging battery that combines a solar cell with a rechargeable battery [10] or a solar-powered electrochemical energy storage (SPEES) system, which integrates a PEC cell and an EC cell into a single device. [9,11] Most SPEES systems are based on the redox reaction between the catholyte and the photoanode or the Solar-intercalation batteries, which are able to both harvest and store solar energy within the electrodes, are a promising technology for the more efficient utilization of intermittent solar radiation. However, there is a lack of understanding on how the light-induced intercalation reaction occurs within the electrode host lattice. Here, an in operando synchrotron X-ray diffraction methodology is introduced, which allows for real-time visualization of the structural evolution process within a solar-intercalation battery host electrode lattice. Coupled with ex situ material characterization, direct correlations between the structural evolution of MoO 3 and the photo-electrochemical responses of the solar-intercalation batteries are established for the first time. MoO 3 is found to transform, via a two-phase reaction mechanism, initially into a sodium bronze phase, Na 0.33 MoO 3 , followed by the formation of solid solutions, Na x MoO 3 (0.33 < x < 1.1), on further photointercalation. Timeresolved correlations with the measured voltages indicate that the two-phase evolution reaction follows zeroth-order kinetics. The insights achieved from this study can aid the development of more advanced photointercalation electrodes and solar batteries with greater performances. Batteries

No abstract

No abstract

-workers report the establishment of a solar-chargeable intercalation battery and an operando synchrotron X-ray diffraction technique that enables realtime tracking of the dynamic structural change of a solar battery electrode from a photo-intercalation reaction. By analyzing the structural prerequisite for light-induced intercalation reaction, novel materials with tailored electrode structures and conductivities can be designed to enhance solar battery technology. BATTERIES